Cooling process employing a heat-actuated regenerative compressor



July 21, 1970 E. G. U. GRANRYD COOLING PROCESS EMPLOYING A HEATACTUATED REGENERATIVE COMPRESSOR Original Filed Dec. 11, 1968 V 2 Sheets-Sheet l INVENTOR Eric G. U Granryd E. G. u. GRANRYD I 3,521,461 coonme PROCESS EMPLOYING A HEAT-ACTUATED w I 4 J REGENERATIVE comrnssson Original Filed Dec. 11, 1 968 2 Sheets-Sheet 2 FIG. 4

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United States Patent Olfice Patented July 21, 1970 3,521,461 COOLING PROCESS EMPLOYING A HEAT- ACTUATED REGENERATIVE COMPRESSOR Eric G. U. Granryd, Slatthallsvagen, Sweden, assignor to Gas Developments Corporation, Chicago, IlL, a corporation of Illinois Original application Dec. 11, 1968, Ser. No. 783,064. Divided and this application July 22, 1969, Ser. No. 843,694

Int. Cl. F25b 1/00 U.S. Cl. 62115 4 Claims ABSTRACT OF THE DISCLOSURE A process for cooling contained exterior atmosphere by a compression-condensation-expansion-evaporation cooling cycle utilizing a heat-actuated regenerative compressor in conjunction with a pneumatic assisted linkage wherein the refrigerant acts upon the linkage providing a lower absolute pressure at the refrigerant side of the linkage than at the heat-actuated regenerative compressor side of the linkage.

CROSS REFERENCE TO RELATED APPLICATIONS This is a division of copending application Ser. No. 783,064, filed Dec. 11, 1968, said 783,064 application being a continuation-in-part of my copending application Ser. No. 698,857, filed Jan. 18, 1968.

BACKGROUND OF THE INVENTION Heretofore, heat actuated regenerative compressors have been used to compress gases for cooling systems. Heatactuated regenerative compressor-cooling systems wherein the refrigerant is also a working fluid of such compressor using carbon dioxide and sulfur dioxide have been described in U.S. Pat. No. 3,400,555 entitled Refrigeration System Employing Heat-Actuated Compressor. Further, such compressors for use in cooling systems have been described in U.S. Pat. No. 3,413,815, entitled Heat-Actuated Regenerative Compressor for Refrigerating Systems. Methods for obtaining mechanical energy from heat-actuated regenerative compressors and dual gas cooling systems wherein the heat-actuated regenerative compressor contains a thermally efficient gas providing energy for moving a highly efiicient refrigerant through a cooling cycle have been described in copending U.S. patent application Ser. No. 698,857. It has now been found desirable, especially in use of heat-actuated regenerative compressors in conjunction with cooling systemsto provide a means for operation of such compressor at a different and higher absolute pressure than the pressure at which the associated cooling system is optimally operated.

DESCRIPTION OF THE INVENTION My invention provides for operation of a heat-actuated regenerative compressor at higher absolute pressures than the absolute operating pressures of external apparatus associated with such a compressor. The process of my invention utilizes pneumatic pressures on linkages between said compressor and associated apparatus to provide a positive pressure in opposition to the pressure of the working gas of the heat-actuated regenerative compressor. The process of my invention is particularly suited to provide cooling systems wherein the heat-actuated regenerative compressor serves through a pressure translating means to pump an eflicient refrigerant through a conventional cooling cycle.

It is an object of my invention to provide an improved cooling process wherein the cooling system is powered by a heat-actuated regenerative compressor wherein the absolute pressure of the working gas in the compressor is always higher than the absolute pressure of the refrigerant.

This and other important objects will become apparent from the drawings showing preferred embodiments wherem:

FIG. 1 is a plan view, in cross section, of a heat-actuated regenerative compressor suitable for use in the process of this invention.

FIG. 2 is a schematic drawing in cross section illustrating the linkage portion of a cooling apparatus suitable for use in the process of this invention driven by a heatactnated regenerative compressor wherein the operating pressure of the power compressor is higher than the operating pressure of the refrigerant.

FIG. 3 illustrates a linkage device according to a preferred embodiment of theapparatus shown in FIG. 2.

FIG. 4 is a graph illustrating the pressure-volume relationships in a process according to an embodiment of this invention.

FIG. 5 is a schematic drawing showing a cooling system according to this invention.

FIG. 6 is a thermodynamic diagram of the cooling system of FIG. 5.

Refrigerants suitable for use in the cooling apparatus suitable for use in the process of my invention include those refrigerants suitable for compression-refrigeration cycles. Preferred refrigerants include halogenated hydro carbons and S0 Particularly preferred refrigerants are those selected from the group consisting of Freon 12, Freon 22, Freon 502 and S0 Freon designates a group of halogenated hydrocarbons containing one or more fluorine atoms which are widely used as refrigerants. The operating conditions and particular refrigerant used determine the pressure and temperature relationships of the closed refrigerating cycle. Under most operating conditions the evaporating temperature is from about 35 to 50 F. and the condensing temperature from about to 150 F., both under constant pressure. Particularly preferred condensing temperatures are from about to F. In conventional air-conditioning systems the pressure ratio, defined as the ratio of the absolute pressure in the condenser and the absolute pressure in the evaporator, is from about 3 to 4 /2 Referring specifically to FIG. 1, the heat-actuated regenerative compressor 1 comprises outer shell casing 2, insulation 4 and inner shell casing 5 defining gas chamher 6 which is generally cylindrical in shape. Shaft 14 is disposed through chamber 6, and retained in suitable rotatable relationship by bearing means. Shaft 14 penetrates casing 5 in fluid tight relationship and is connected through suitable linkage means to a power source (not shown) which causes shaft 14 to undergo an oscillating movement. Secured to shaft 14 is insulating hub 18 having vane 20 constructed of suitable support thermal insulating material extending to and congruent with inner shell casing 5.

Vane 20 divides chamber 6 into a first cold" section 19 and a second hot section 21. Positioned within chamber 6 from inner shell casing toward the center of chamber 6 to hub 18 extending substantially the entire length of chamber 6 separating cold section 19 from hot section 21 are cooling means 22, heat regenerative means 23, and heating means 24. The sizes of such components shown in FIG. 1 and described above are based upon current heat transfer materials, designs, and techniques, however, it would be apparent to one skilled in the art that if more efficient heat transfer units becomes available, the size proportions and shapes of the heat transfer units could readily be changed accordingly. The large hub 18 and insulator 25 provide a long travel distance insulating cold section 19 from hot section 21 at the heat exchangers.

Briefly, operation of the compressor is achieved by moving gas from cold section 19 in order through the cooler-regenerator-heater into hot section 21 at an average higher temperature-pressure relationship and then returning the gas from hot section 21 in order back through the heater-regenerator-cooler to cold section 19 at an average lower temperature-pressure relationship. Vane frequencies of from about 15 to 500 cycles per minute are suitable for the compressor of this invention. Preferred frequencies are from about 100 to 300 cycles per minute.

The heat actuated compressor is operated by use of gases having high thermal-conductivity and specific heat ratio. Preferred gases include hydrogen and monatomic inert gases such as helium. Either a single gas or mixtures of different gases may be used. Helium is especially preferred for use in the heat-actuated regenerative compressor according to this invention.

In FIG. 1 differential pressure means comprises a pneumatic, hydraulic or mechanical assisted linkage to associated apparatus providing lower absolute pressures at the side of the linkage connected to such apparatus than at the side of the linkage in communication with the heat-actuated compressor. Combinations of such assistance may be used, for example, the assistance may be pneumatic and mechanical in combination. Specific embodiments illustrating such pressure responsive means are illustrated by further figures and description. The differential pressure means may be in communication with cold section 19 in the region of the cooler, or between the cooler and regenerator, but may be at either end or through the side of the heat-actuated regenerative compressor containment vessel.

FIG. 1 shows specific embodiments of the heat-actuated regenerative compressor which result in surprising improvements in its operation, as compared with the prior devices. Thin vane 20, constructed of materials affording thermal insulating properties, is especially effective in the rapid movement of the working gas of the compressor from cold section 19 through the three heat transfer units to hot section 21. Operation of vane 20 at frequencies in the order of 200 cycles per minute affords especially efiicient transfer of thermal energy in the heater, regenerator and cooler thermal transfer units in the oscillating manner utilized in this apparatus. Due to the physical configuration of the components in the active chamber of the heat-actuated regenerative compressor, the sweep of the oscillating vane may vary from about 180 to 250 degrees depending upon the efficiency of the thermal transfer units, gas utilized, and frequency of operation desired.

The pressure ratio of the heat-actuated regenerative compressor, defined as the ratio of the maximum absolute pressure in the compressor to the minimum absolute pressure in the compressor, is determined by the mass mean temperature ranges operable using desired gases in the heat-actuated regenerative compressor. Pressure ratios in heat-actuated regenerative compressors range from about 1.0 to 1.8.

Required pressure ratios for operating various desired apparatus are frequently different from the pressure ratio of the direct output of the heat-actuated regenerative compressor. One such application is in the powering of cooling systems with a heat-actuated regenerative compressor. As pointed out above, the pressure ratio in conventional cooling systems is between 3 and 4 /2 while the pressure ratio in the heat-actuated regenerative compressors is from about 1.3 to about 1.8. One feature of the present invention is to provide differential pressure linkage means between the heat-actuated regenerative compressor and associated apparatus, such as cooling systems thereby making possible the use of one-stage heat-actuated compressor systems. The linkage pressure differential is preferable constant throughout one cycle of the heat-actuated regenerative compressor, but may be variable within the period of one cycle of the heat-actuated regenerative compressor.

FIG. 2 shows the pneumatic linkage portion of an apparatus suitable for the cooling process of this invention wherein the linkage between the piston for compression of the refrigerant and the output of the heat-actuated regenerative compressor driving the cooling unit is assisted by the pressure of the refrigerant to enable operation of the heat-actuated regenerative compressor at higher absolute pressures than the refrigerant. Piston 60 having face 61 in communication with cold section 19 is mounted for reciprocating action in cylinder chamber 62 defined by cylinder wall 63. Cylinder chamber 62 is maintained in gas-tight relationship with cold section 19 by bellows 34.

Bellows 34 must be constructed of suitable material and of suitable design to permit the required flexing and expansion while at the same time maintaining gas-tight relationship between cold section 19 and cylinder chamber 62. Metal bellows are most satisfactory using copper, nickel and various stainless steel alloys or mixtures of copper and nickel. It is also apparent that other flexible materials such as certain rubber or synthetic materials may be used if they do not permit diffusion of gases between cold section 19 and cylinder chamber 62. Suitable bellows are available commercially.

Face 74 of piston 60 is in communication with cylinder chamber 62, which in turn is in communication with conduit 71. Piston 60 is rigidly attached to connecting rod 64 which passes in gas-tight relationships to compression chamber 65 defined by compression chamber walls 66. Compression piston 67 is rigidly connected to the opposite end of connecting rod 64 from piston 60, and moves in reciprocating action in generally gas-tight relationship Within compression chamber 65. Conduit 68 is in communication with the evaporator of the cooling cycle and splits the flow of refrigerant gas between inlet valve 69 opening to compression chamber 65 and thereby in communication with face 72 of piston 67 and the opposite face 73 of piston 67 providing the refrigerant evaporation pressure to face 73. Communication of both sides of piston 67 with refrigerant gas in conduit 68 minimizes the requirement for high quality seals between piston 67 and compression chamber walls 66. The configuration also eliminates having connections to the atmosphere or to a vacuum chamber. Such an arrangement of components permits. a completely hermetically sealed compressor unit for use in air conditioning systems.

The refrigerant is compressed by action of piston 67 in compression chamber 65 and the compressed refrigerant exists through outlet valve to conduit 71. Conduit 71 is in communication with the condenser of the cooling cycle and with face 74 of piston 60. A constant resistant force corresponding to the refrigerant condenser pressure acts on face 74 of piston 60. Such resistant force permits operation of the heat-actuated regenerative compressor in communication with face 61 of piston 60 at higher absolute pressures than the refrigerant pressure in the cooling apparatus. The force on piston 60 may be reduced by the relative size of connecting rod 64 and piston face 74.

By the configuration of components shown in FIG. 2, the condenser pressure of the refrigerant is utilized to furnish pneumatic assistance to the linkage between a heat-actuated regenerative compressor and associated cooling apparatus, permitting operation of the driving compressor at higher absolute pressure than the pressures of the refrigerant.

FIG. 2 shows pistons 60 and 67 in full line position A at the end of the full refrigerant compressor suction stroke and by dotted line at the opposite extreme position at the end of the refrigerant compression stroke, position B.

FIG. 3 shows a cross-section of a preferred embodiment of the pneumatic linkage shown schematically in FIG. 2. The same numerals used for components shown in FIG. 2 are applied to corresponding components in FIG. 3. FIG. 3 additionally shows seal 75 in compression chamber 65 providing a gas-tight seal between piston 67 and cylinder walls 66. Seal 75 comprises a reinforced rubber diaphragm providing a gas-tight and pressure-tight seal with minimum friction. One suitable seal commercially available is known as Bellofram seal. Due to operation of such diaphragm seals, it is preferred that connecting rod 64 be in a vertical position.

It should be apparent that the term piston as used in the description and claims includes various shapes and mechanisms providing for reciprocating motion within a confined chamber and is meant as used herein to include diaphragms, bellows, and the like.

Referring to FIG. 4, the pressure-volume relationships of the cooling process of this invention utilizing the apparatus of FIGS. 2 and 3 are shown using helium as the working gas in the power unit (heat-actuated regenerative compressor as shown in FIG. 1) and Freon 22 as the refrigerant in the cooling unit. This is one preferred embodiment of gases suitable for use in the apparatus shown in FIGS. 2 and 3. The point A for the refrigerant compressor cycle and A for the power cycle correspond to position shown by the full-line representation in FIG. 2-. This shows the position of the pistons at the end of the full refrigerant compressor suction stroke and corresponding pressure-volume relationships. The point B for the refrigerant compressor cycle and B for the power cycle on the graphs correspond to the position shown by the dotted line representation in FIG. 2. This shows the position of the pistons at the end of the full refrigerant compression stroke and corresponding pressure-volume relationships.

It is readily observed from FIG. 4 that the pressure ratio of the working gas in the power cycle is nearly 1.8 and the pressure ratio of the refrigerant in the cooling cycle is 3.8. It is also apparent that the pressure ratio of the power cycle can be chosen to other levels, if desired, by appropriate sizing of relative areas of pistons 60 and 67. The pressure ratio of the cooling cycle is dependent upon the refrigerant, and, for example, using Freon 22 as refrigerant, the refrigerant pressure ratio of about 3.8 can be achieved by a single stage heatactuated regenerative compressor unit. Prior methods not using the assisted linkage of this invention required multiple stages of heat-actuated regenerative compressor outputs to achieve the required pressure ratio for the most desirable refrigerants. FIG. 4 further illustrates that it is desirable to operate the pneumatic linkage in a fashion so that it continuously maintains a constant pressure differential between the working gas of the heatactuated regenerative compressor and the working refrigerant. This is evident from the notations of P as shown in FIG. 4. The economic savings and space savings resulting from the cooling apparatus of this invention are readily apparent. Air-conditioning units according to this invention suitable for residential use are also obtained.

FIG. 5 shows a complete cooling system according to my invention wherein represents a heat-actuated regenerative compressor power unit as shown in one embodiment in FIG. 1, the heat-in represents thermal energy added to the active gas of the power unit compressor by the internal heater, and the heat-out represents thermal energy removed from the active gas of such compressor by the internal cooler. Heat-actuated regenerative compressor 80 is in communication with refrigerant compressor 82 through a pneumatic assisted linkage 81 providing lower absolute pressures at the refrigerant compressor 82 side of the linkage than at the power. unit 80 side of the linkage. The heat-actuated regenerative compressor 80 through linkage 81, such as shown in specific embodiments FIGS. 2 and 3 powers refrigerant compressor 82 driving refrigerant through a c0ndensation-expansion-evaporation-compression cooling cycle.

The states of the refrigerant shown in FIG. 5 as letters correspond to the letters on the thermodynamic diagram shownin FIG. 6. Refrigerant gas flows from refrigerant compressor 82 at state F through condenser 83 removing heat from the refrigerant to the ambient atmosphere, flowing from condenser 83 at state G as a liquid, through expansion throttle 84 reducing the pressure to state H, and through evaporator 85 wherein heat is taken up from the exterior cooled atmosphere and re-entering the heat-actuated regenerative compressor at state E for compression. Evaporator 85 represents the cooling of confined room air in the case of a room air conditioning unit.

Referring particularly to FIG. 2, one important embodiment of my invention is the provision of an improved cooling system powered by a heat-actuated regenerative compressor wherein the absolute pressure of the working gas in the compressor is always higher than the absolute pressure of the refrigerant. My invention includes a process for cooling contained exterior atmosphere by a compression-condenser-expansionevaporation cooling cycle comprising the steps of compressing contained gaseous refrigerant by a second piston driven by a first piston, one side of the first piston being in communication with the active volume of a heat-actuated regenerative compressor and the other side of the first piston in communication with the contained gaseous refrigerant at condenser pressure of the cooling cycle. The process of my invention renders compact heat-actuated regenerative compressor driven cooling systems practical from the standpoint of economics, space requirements and overall efficiency. Cooling systems, according to my process, are readily obtained when the pressure ratio of the heat-actuated regenerative compressor is from about 1.3 to 1.8 and the pressure ratio of the cooling cycle is from 3.0 to 4.5. Cooling apparatus suitable for residential uses are obtained by the process of my invention.

While in the foregoing specification this invention has been described in relation to certain preferred embodiments thereof, and many details have been set forth for purpose of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the invention.

I claim:

1. In a process for cooling contained exterior atmosphere by a compression-condensation-expansion-evaporation cooling cycle, the improvement comprising the steps of compressing contained gaseous refrigerant by a second piston driven by a first piston, one side of said first piston in communication with the active volume of a heatactuated regenerative compressor and the other side of said first piston in communication with the contained gaseous refrigerant at condenser pressure of said cooling cycle.

8 2. The process of claim 1 wherein said refrigerant is ahalogenated hydrocarbon. References Cited 3. The process of claim 1 wherein the absolute pres- UNITED STATES PATENTS sure of said cooling cycle is less than the absolute pres- 2,991,632 7/1961 Rogers 62498 sure of the actlve gas of sand heat-actuated regenerative 5 3,101,597 8/1963 Dros compressor.

4. The process of claim 1 wherein the pressure ratio MEYER PERLIN Primary Examiner of the heat-actuated regenerative compressor is from about 1.3 to 1.8 and the pressure ratio of the cooling CL cycle is from about 3.0 to 4.5. 62 6 4 

